<html>
<script>
function foo1(a){
    return a + '01';
}

var a1 = foo1(01);

function foo2(a){
    return a + '010';
}

var a2 = foo2(010);
console.log(a1); //101
console.log(a2); // 8010
console.log(0.2 + 0.4);

var a3 = ++[[]][+[]]+[+[]];

console.log(a3); //10
console.log(0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1);
</script>
</html>